For some time now, it has become commonplace for manufacturers of drugs, medicines and other substances which must be utilized with care to provide containers thereof with child-resistant caps or closure means. These are now available in a variety of designs and most require the user to push on an outer element of a multicomponent cap, require the alignment of visible marks, or require the user to squeeze portions of the outer cap to cause engagement with an inner cap portion that is directly threaded on to the container so as to engage the two during unscrewing or opening of the container. There are many situations where, primarily because there are no young children around to accidentally open such containers and ingest their contents, it is highly desirable to place such a child-resistant cap in a mode in which it is non-child-resistant, i.e., it functions simply as a cap that can be threaded or unthreaded onto a container without pressing or squeezing by the user. Various designs have been proposed for this purpose.
U.S. Pat. No. 4,271,971 to Morris, for example, proposes a three-component safety cap for threaded containers, the cap having a rotational actuator element which can be threaded into an inner cap element to permanently engage the same with an outer cap element so that the two become nonrotationally engaged with each other. The rotational actuator element can be unthreaded to reverse this action so as to set the inner and outer caps rotationally free of each other and return the device to its child-resistant mode of operation.
U.S. Pat. No. 4,281,771 to Siegel discloses a child-resistant closure device having an inner cap and an outer cap which can be rotationally locked to each other by the insertion of a user-applied plug passed through an aperture of the outer cap to engage a raised circumferential lug in the inner cap. Removal of the plug by the user reverses this process and renders the closure child-resistant.
U.S. Pat. No. 4,433,789 to Gibilisco, on the other hand, discloses a two-part child-resistant closure in which an outer cap selectively engageable with an inner cap threaded directly to the container can be simply torn off, thereby leaving the inner cap to function as a conventional non-child-resistant cap.
In yet another variation, U.S. Pat. No. 4,553,678 to Thorsbakken discloses a safety cap assembly for bottles, i.e., a child-resistant closure device of the "push-to-turn" type, in which the tearing out or removal of a biasing element between an inner cap and an outer cap rotationally locks the two to render the device non-child-resistant.
The exemplary devices discussed in the immediately preceding paragraphs, while accomplishing a function generally similar to that of the present invention, have various limitations, e.g., they require the user either to add something to the device (such as the removable plug of Siegel) or remove something from the device (the entire outer cap of Gibilisco) or require a definite effort on the part of the user to render the device non-child-resistant (the deliberate threading-in of the rotational actuator element of Morris). There is, therefore, a clear need for a simple child-resistant closure device that may be readily placed in a non-child-resistant mode by a user without the need for adding to or removing parts from the device. The present invention fills this need by providing a child-resistant safety cap which can be rendered permanently and irreversibly non-child-resistant by a single simple action by the user, typically a pharmacist dispensing medication.